1. Field of the Invention
The present invention relates to an XY-positioning table, more specifically, to an XY-positioning table consisting of a lower table and an upper table relatively movable therewith and for use in accurately positioning the upper table to the lower table thereby to precisely indexing the tools secured on the upper table onto workpieces, in which the inertial force taking place upon the movement of the tables can be reduced thereby to improve accuracy of positioning or indexing of both the tables relative to each other as well as the workpieces.
2. Description of the Prior Art
As a prior art is disclosed by, for example, Japanese Utility Model Application Disclosure No. 44144-1983, an XY-positioning table device consisting of an upper table and a lower table and designed to reduce the inertial force taking place upon the movement of the lower table relative to the device by decreasing the load imposed on to the lower table by means of a simple mechanism. In the above-mentioned device, however, such a simple mechanism as mentioned above is provided outside the table so as to prevent the weight of the driving motor for the upper table from being borne by the lower table, thus not only greatly increasing the whole dimension of the XY-positioning table but also forming not a small barrier in its miniaturization.
Further the above-mentioned prior X-Y positioning device adopts a construction in which the positioning of the upper table relative to the lower table is effected by means of a follower-type bearing means provided on both sides of guide rail means, hence, when the upper table is moved, the accuracy in indexing or positioning of the upper table relative to the lower table is greatly influenced by accuracy of the relevant bearing means, accuracy of guide rail means, and gap between the bearing means and the guide rail means so on, thus giving rise to a problem of accuracy in positioning or indexing of the tables.